Apex domains cannot have CNAME records.
Question and response
Question
dig smartrefill.se. NS
Answer
smartrefill.se. 5 NS dns3.oderland.com.
smartrefill.se. 5 NS dns2.oderland.com.
smartrefill.se. 5 NS dns1.oderland.com.
Authority
The response has no authority records.
Additional
. 0 OPT ; payload 1232, xrcode 0, version 0, flags 0